Springs in a flashlight allow the light to stay on if/when dropped or given a hard shock… that is the defining purpose.

There are quite a few “crusher” style lights out there that work perfectly with a given cell, do you think everyone that buys those lights buys the specified cell to go with it? If Jack sold a proprietary cell alongside the PL47 and guaranteed it’s fitment, you can rest assured a great many would take a pass on that cell in favor of their own… it’s all part of designing lights to be as compact as possible to gain favor with a particular market group, much like the DQG lights.

It is form that follows function, not the other way around.